Field studies were conducted in 1993 to investigate a possible sexual dimorphism in the elytra coloration pattern of western com rootworm,Diabrotica virgifera virgiferaLeConte, adults, and to compare the sex ratio of adults captured on 2 types (Olson and Pherocon AM) of commercial yellow sticky traps with those obtained by aspiration. Striped and solid variationsin elytra pattern were found in both sexes. Of the western corn rootworm adults that exhibited the solid elytra pattern,>99% captured on yellow stickytraps and 97% collected by aspiration were male. In contrast, of those adults which exhibited the striped elytra pattern, 79% captured on yellow stickytraps and 42% collected by aspiration were male. Sex ratio of adults varied significantly over time and among sampling methods. Sticky traps captured a significantly greater proportion of males compared with aspiration. No significant difference in sex ratio was found between the 2 types of sticky traps; however,the Olson trap captured significantly more com rootworm adults overall than the modified Pherocon AM trap.